fix(datepicker): update popup direction if datepicker direction changes

src/lib/datepicker/datepicker.spec.ts

@@ -29,6 +29,7 @@ import {MatDatepickerInput} from './datepicker-input';
 import {MatDatepickerToggle} from './datepicker-toggle';
 import {MAT_DATEPICKER_SCROLL_STRATEGY, MatDatepickerIntl, MatDatepickerModule} from './index';
 import {Subject} from 'rxjs';
+import {Directionality} from '@angular/cdk/bidi';
 
 describe('MatDatepicker', () => {
   const SUPPORTS_INTL = typeof Intl != 'undefined';
@@ -1268,6 +1269,68 @@ describe('MatDatepicker', () => {
       }));
     });
 
+    describe('datepicker directionality', () => {
+      it('should pass along the directionality to the popup', () => {
+        const fixture = createComponent(StandardDatepicker, [MatNativeDateModule], [{
+          provide: Directionality,
+          useValue: ({value: 'rtl'})
+        }]);
+
+        fixture.detectChanges();
+        fixture.componentInstance.datepicker.open();
+        fixture.detectChanges();
+
+        const overlay = document.querySelector('.cdk-overlay-pane')!;
+
+        expect(overlay.getAttribute('dir')).toBe('rtl');
+      });
+
+      it('should update the popup direction if the directionality value changes', fakeAsync(() => {
+        const dirProvider = {value: 'ltr'};
+        const fixture = createComponent(StandardDatepicker, [MatNativeDateModule], [{
+          provide: Directionality,
+          useFactory: () => dirProvider
+        }]);
+
+        fixture.detectChanges();
+        fixture.componentInstance.datepicker.open();
+        fixture.detectChanges();
+
+        let overlay = document.querySelector('.cdk-overlay-pane')!;
+
+        expect(overlay.getAttribute('dir')).toBe('ltr');
+
+        fixture.componentInstance.datepicker.close();
+        fixture.detectChanges();
+        flush();
+
+        dirProvider.value = 'rtl';
+        fixture.componentInstance.datepicker.open();
+        fixture.detectChanges();
+
+        overlay = document.querySelector('.cdk-overlay-pane')!;
+
+        expect(overlay.getAttribute('dir')).toBe('rtl');
+      }));
+
+      it('should pass along the directionality to the dialog in touch mode', () => {
+        const fixture = createComponent(StandardDatepicker, [MatNativeDateModule], [{
+          provide: Directionality,
+          useValue: ({value: 'rtl'})
+        }]);
+
+        fixture.componentInstance.touch = true;
+        fixture.detectChanges();
+        fixture.componentInstance.datepicker.open();
+        fixture.detectChanges();
+
+        const overlay = document.querySelector('.cdk-overlay-pane')!;
+
+        expect(overlay.getAttribute('dir')).toBe('rtl');
+      });
+
+    });
+
   });
 
   describe('with missing DateAdapter and MAT_DATE_FORMATS', () => {

src/lib/datepicker/datepicker.ts

@@ -422,14 +422,13 @@ export class MatDatepicker<D> implements OnDestroy, CanColor {
   /** Open the calendar as a dialog. */
   private _openAsDialog(): void {
     this._dialogRef = this._dialog.open<MatDatepickerContent<D>>(MatDatepickerContent, {
-      direction: this._dir ? this._dir.value : 'ltr',
+      direction: this._getDirection(),
       viewContainerRef: this._viewContainerRef,
       panelClass: 'mat-datepicker-dialog',
     });
-    if (this._dialogRef) {
-      this._dialogRef.afterClosed().subscribe(() => this.close());
-      this._dialogRef.componentInstance.datepicker = this;
-    }
+
+    this._dialogRef.afterClosed().subscribe(() => this.close());
+    this._dialogRef.componentInstance.datepicker = this;
     this._setColor();
   }
 
@@ -445,6 +444,7 @@ export class MatDatepicker<D> implements OnDestroy, CanColor {
     }
 
     if (!this._popupRef.hasAttached()) {
+      this._popupRef.setDirection(this._getDirection());
       this._popupComponentRef = this._popupRef.attach(this._calendarPortal);
       this._popupComponentRef.instance.datepicker = this;
       this._setColor();
@@ -462,7 +462,7 @@ export class MatDatepicker<D> implements OnDestroy, CanColor {
       positionStrategy: this._createPopupPositionStrategy(),
       hasBackdrop: true,
       backdropClass: 'mat-overlay-transparent-backdrop',
-      direction: this._dir ? this._dir.value : 'ltr',
+      direction: this._getDirection(),
       scrollStrategy: this._scrollStrategy(),
       panelClass: 'mat-datepicker-popup',
     });
@@ -533,4 +533,9 @@ export class MatDatepicker<D> implements OnDestroy, CanColor {
       this._dialogRef.componentInstance.color = color;
     }
   }
+
+  /** Returns the layout direction of the datepicker. */
+  private _getDirection() {
+    return this._dir ? this._dir.value : 'ltr';
+  }
 }